Total hip arthroplasty in acetabular protrusio.

Protrusio is a central acetabular defect resulting from migration of the femoral head medial to Kohler's line. Protrusio can develop in association with a number of conditions that affect the metabolism or mechanical behavior of the periacetabular bone. Total hip arthroplasty (THA) for acetabular protrusio requires reconstruction of the contained cavitary defect. The acetabular rim is generally intact. The defect can be effectively treated with a lateralized cementless porous-coated component supported on the peripheral acetabular bony rim. Morsellized autograft is used to fill the medial defect. However, if the rim is inadequate to provide mechanical support for a cementless cup due to bone loss or osteoporosis, cementless cup reconstruction can result in medial migration. If rim support is inadequate, a reconstruction cage is a more appropriate option to gain fixation to the pelvis above and below the acetabulum. Total hip arthroplasty for protrusio can also affect both offset and leg length, so careful preoperative templating is important to help determine implant position. Results of THA with medial acetabular bone grafting for protrusio acetabuli have been favorable, with success rates similar to conventional THA.